You can open an image context, and then harvest its content immediately, without drawing anything into it. This should produce a blank `36x36` `UIImage`:

    UIGraphicsBeginImageContextWithOptions(CGSizeMake(36, 36), NO, 0.0);
    UIImage *blank = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

```swift
let img = UIImage() // size does not matter for a blank transparent image
```
When using a blank transparent image, its size does not matter, and I think the `imageView.contentMode` might be any scalable value, or set it to `UIView.ContentMode.scaleAspectFit` or `UIView.ContentMode.scaleAspectFill` if needed.


In the stack trace of my iPhone application, I see a call to something called `PurpleEventCallback`. I wasn&#39;t able to find any documentation for it. What is this?

![PurpleEventCallback][1]

  [1]: http://i.stack.imgur.com/x9uwi.png

What is PurpleEventCallback?

I would like to exclude these albums, that has name:

    $ban_album_names = array(&#39;Wall&#39;, &#39;Profile&#39;, &#39;Cover&#39;, &#39;Instagram&#39;);

How do I write correctly,

    SELECT * FROM albums WHERE name NOT IN ???

How can I make it look in the array, and if the name matches it should != the row

MySQL where NOT IN name array?

How can I create a blank png UIImage in Objective C programmatically (let&#39;s say 36x36 px)?

Thanks :)

How to create a blank transparent png in Objective-C?

<p>How can I create a blank png UIImage in Objective C programmatically (let's say 36x36 px)?</p>
<p>Thanks :)</p>


I&#39;ve seen several posts on google and stackoverflow related to this error, I&#39;ve read all of them but still fetching the problem , I will be glad for a solution. Here is the error mesage I recieve when compiling ...

&gt; directory not found for option &#39;-L/Users/somefolder/Documents/Bharat/MyApp copy/GoogleAdMobAdsSDK&#39;
duplicate symbol _OBJC_CLASS_$_AppDelegate in:
    /Users/madept/Library/Developer/Xcode/DerivedData/Alpha-dvvymdlmzseytagllsmbbrxdgutz/Build/Intermediates/Alpha.build/Debug-iphonesimulator/Alpha.build/Objects-normal/i386/AppDelegate-56890B6B994A4284.o

Thanks.

duplicate symbols for architecture i386 clang

I&#39;ve been using `enumerateObjectsUsingBlock:` a lot lately for my fast-enumeration needs, and I&#39;m having a hard time understanding the usage of `BOOL *stop` in the enumeration block.

The `NSArray` class reference states

&gt; `stop`: A reference to a Boolean value. The block can set the value to `YES` to
&gt; stop further processing of the array. The `stop` argument is an out-only
&gt; argument. You should only ever set this Boolean to `YES` within the
&gt; Block.

So then of course I can add the following in my block to stop the enumeration:


    if (idx == [myArray indexOfObject:[myArray lastObject]]) {
        *stop = YES;
    }

From what I&#39;ve been able to tell, not explicitly setting `*stop` to `YES` doesn&#39;t have any negative side effects. The enumeration seems to automatically stop itself at the end of the array. So is using `*stop` really necessary in a block?

What is the BOOL *stop argument for enumerateObjectsUsingBlock: used for?

I upgraded [Xcode][1] version and when using external static libraries, I get this message:

&gt; ld: file is universal (3 slices) but does not contain a(n) armv7s slice: /file/location for architecture armv7s
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Is there any way to bypass this and add support to the library if the developer of the library hasn&#39;t updated their library yet?

  [1]: http://en.wikipedia.org/wiki/Xcode


File is universal (three slices), but it does not contain a(n) ARMv7-s slice error for static libraries on iOS, anyway to bypass?

I have just installed Xcode 4.5 for iOS6 support, and I have seen a new icon called &#39;Exit&#39; in my Storyboard, listed under my view controllers along with &#39;First Responder&#39; etc. A little green icon labeled &#39;Exit&#39;.

I can find anything about it, nor work out how it can be used. How does it work?


Xcode 4.5 Storyboard &#39;Exit&#39;

I know I can create an `NSArray` with `@[@&quot;foo&quot;, @&quot;bar&quot;]` or an `NSDictionary` with `@{@0 : @&quot;foo&quot;, @1 : @&quot;bar&quot;}`.

Is there a literal syntax for creating an `NSMutableArray` or an `NSMutableDictionary`?

Is there a literal syntax for mutable collections?

I&#39;m using MGSplitViewController and I&#39;m using`shouldAutorotateToInterfaceOrientation` to control the size of the master view controller on rotation. 

It&#39;s all working fine on iOS 5 but on iOS 6 (both simulator and iPad) `shouldAutorotateToInterfaceOrientation` is never called.

Is this a bug that I should expect to be fixed with the final release of iOS 6 or something that I&#39;m not aware of has changed?

shouldAutorotateToInterfaceOrientation not being called in iOS 6

In Apple&#39;s AppStore Terms &amp; Conditions, you may find the following statement in relation to Auto-renewable In App Purchases:

&gt;&quot;Certain paid In App Subscriptions may offer a free trial period prior to charging your Account.&quot;

How does it work? I haven&#39;t seen any option to allow such free trial period for my Auto-renewable IAPs in iTunes Connect.

How to set-up In App Purchase free trial period in iOS app

Is it possible to control UIView border properties (color, thickness, etc...) directly from interface builder or I can only do it programmatically?

Is it possible to set UIView border properties from interface builder?

What is the ***iOS 6.0*** user agent string?

----------

Previous user-agent strings:

 - [**iOS 5.1** - What is the iOS 5.1 user agent string?][1]
 - [**iOS 5.0** - What is the iOS 5.0 user agent string?][2]
 - [**iOS 4.0** - What is the iPhone 4 user-agent?][3]


  [1]: https://stackoverflow.com/q/10152433/836407
  [2]: https://stackoverflow.com/q/7825873/836407
  [3]: https://stackoverflow.com/q/3105555/836407


What is the iOS 6 user agent string?

I&#39;m trying to change color of UIImage. My code:

    -(UIImage *)coloredImage:(UIImage *)firstImage withColor:(UIColor *)color {
        UIGraphicsBeginImageContext(firstImage.size);
    
        CGContextRef context = UIGraphicsGetCurrentContext();
        [color setFill];
    
        CGContextTranslateCTM(context, 0, firstImage.size.height);
        CGContextScaleCTM(context, 1.0, -1.0);
    
        CGContextSetBlendMode(context, kCGBlendModeCopy);
        CGRect rect = CGRectMake(0, 0, firstImage.size.width, firstImage.size.height);
        CGContextDrawImage(context, rect, firstImage.CGImage);
    
        CGContextClipToMask(context, rect, firstImage.CGImage);
        CGContextAddRect(context, rect);
        CGContextDrawPath(context,kCGPathElementMoveToPoint);
    
        UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    
        return coloredImg;
    }
This code works, but obtained image is not so well as shoud be: bounds pixels of returned image are intermittent and not so smooth as in my first image. How can I resolve this problem?

Changing UIImage color

I must add a UIImageView as subview of MapView. To do this I created a layer above the MapView. In this layer I want to put my image, but I get a white rectangle and nothing else. My image is not visible.

This is the code:

    - (void)viewDidLoad
    {
        //......

        CALayer *layer = [CALayer layer];
        layer.backgroundColor = [[UIColor whiteColor] CGColor];
   
        if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)
        {
            layer.bounds = CGRectMake(self.mapView.bounds.origin.x,
                                      self.mapView.bounds.origin.y, 80, 300);
        }
        else
        {
            layer.bounds = CGRectMake(self.mapView.frame.origin.x,
                                      self.mapView.frame.origin.y, 150, 700);
        }
    
        layer.contents = (id)[UIImage imageNamed:@&quot;myImage.png&quot;];
        //the name is correct but  in the output the image is not visible
    
        [[self.mapView layer] addSublayer:layer];
        [layer setNeedsDisplay];
    }


add UIImage in CALayer

I&#39;ve been using `UIGraphicsBeginImageContextWithOptions()` and I noticed that the last field in that method is a `scalefactor`. And the apple docs says, if I want to set it to 0.0, then it will use the default scale factor of the device&#39;s main screen. Is there a way to get that default scale factor via property or method?

How to get the device&#39;s scale factor?

I have an image view, declared programmatically, and I am setting its image, also programmatically.

However, I find myself unable to set the image to both fit the aspect and align centre to the image view.

In other words, I want the image to:

- Scale down to fit the aspect, if the image is large.
- Centre but not scale up, if the image is small.

How do I get that?

UIImageView aspect fit and center

I am using the following code for an image picker. But when I run it in the simulator, I have a memory leak and I get a warning about `presentModalViewcontroller:animated` being deprecated in iOS6. I also get `dismissModalViewController:animated` deprecated. I&#39;m using the SDK 6.1.

Code for ImagePicker:


    - (void)showAlbum:(id)sender { 
        imagePicker=[[UIImagePickerController alloc]init];
        imagePicker.delegate = self;
        imagePicker.allowsEditing =NO;
        imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        [self presentModalViewController:imagePicker animated:YES];
    }
    
    - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{
        //release picker
        [picker dismissModalViewControllerAnimated:YES];
    }



Content Type	Original Author	Original Content on Stackoverflow
Question	Nili	View Question on Stackoverflow
Solution 1 - Objective C	Sergey Kalinichenko	View Answer on Stackoverflow
Solution 2 - Objective C	DawnSong	View Answer on Stackoverflow

How to create a blank transparent png in Objective-C?

Objective C Problem Overview

Objective C Solutions

Solution 1 - Objective C

Solution 2 - Objective C

MySQL where NOT IN name array?

What is PurpleEventCallback?

Attributions